package org.apache.lucene.index;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.document.Document;
import org.apache.lucene.document.FieldSelector;
import org.apache.lucene.store.Directory;
import org.apache.lucene.util.MapBackedSet;

import java.io.IOException;
import java.util.Collection;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**  A <code>FilterIndexReader</code> contains another IndexReader, which it
 * uses as its basic source of data, possibly transforming the data along the
 * way or providing additional functionality. The class
 * <code>FilterIndexReader</code> itself simply implements all abstract methods
 * of <code>IndexReader</code> with versions that pass all requests to the
 * contained index reader. Subclasses of <code>FilterIndexReader</code> may
 * further override some of these methods and may also provide additional
 * methods and fields.
 * <p><b>Note:</b> The default implementation of {@link FilterIndexReader#doOpenIfChanged}
 * throws {@link UnsupportedOperationException} (like the base class),
 * so it's not possible to reopen a <code>FilterIndexReader</code>.
 * To reopen, you have to first reopen the underlying reader
 * and wrap it again with the custom filter.
 */
public class FilterIndexReader extends IndexReader {

    /** Base class for filtering {@link TermDocs} implementations. */
    public static class FilterTermDocs implements TermDocs {
        protected TermDocs in;

        public FilterTermDocs(TermDocs in) {
            this.in = in;
        }

        public void seek(Term term) throws IOException {
            in.seek(term);
        }

        public void seek(TermEnum termEnum) throws IOException {
            in.seek(termEnum);
        }

        public int doc() {
            return in.doc();
        }

        public int freq() {
            return in.freq();
        }

        public boolean next() throws IOException {
            return in.next();
        }

        public int read(int[] docs, int[] freqs) throws IOException {
            return in.read(docs, freqs);
        }

        public boolean skipTo(int i) throws IOException {
            return in.skipTo(i);
        }

        public void close() throws IOException {
            in.close();
        }
    }

    /** Base class for filtering {@link TermPositions} implementations. */
    public static class FilterTermPositions extends FilterTermDocs implements TermPositions {

        public FilterTermPositions(TermPositions in) {
            super(in);
        }

        public int nextPosition() throws IOException {
            return ((TermPositions) this.in).nextPosition();
        }

        public int getPayloadLength() {
            return ((TermPositions) this.in).getPayloadLength();
        }

        public byte[] getPayload(byte[] data, int offset) throws IOException {
            return ((TermPositions) this.in).getPayload(data, offset);
        }

        // TODO: Remove warning after API has been finalized
        public boolean isPayloadAvailable() {
            return ((TermPositions) this.in).isPayloadAvailable();
        }
    }

    /** Base class for filtering {@link TermEnum} implementations. */
    public static class FilterTermEnum extends TermEnum {
        protected TermEnum in;

        public FilterTermEnum(TermEnum in) {
            this.in = in;
        }

        @Override
        public boolean next() throws IOException {
            return in.next();
        }

        @Override
        public Term term() {
            return in.term();
        }

        @Override
        public int docFreq() {
            return in.docFreq();
        }

        @Override
        public void close() throws IOException {
            in.close();
        }
    }

    protected IndexReader in;

    /**
     * <p>Construct a FilterIndexReader based on the specified base reader.
     * Directory locking for delete, undeleteAll, and setNorm operations is
     * left to the base reader.</p>
     * <p>Note that base reader is closed if this FilterIndexReader is closed.</p>
     * @param in specified base reader.
     */
    public FilterIndexReader(IndexReader in) {
        super();
        this.in = in;
        readerFinishedListeners = new MapBackedSet<ReaderFinishedListener>(new ConcurrentHashMap<ReaderFinishedListener, Boolean>());
    }

    @Override
    public Directory directory() {
        ensureOpen();
        return in.directory();
    }

    @Override
    public TermFreqVector[] getTermFreqVectors(int docNumber) throws IOException {
        ensureOpen();
        return in.getTermFreqVectors(docNumber);
    }

    @Override
    public TermFreqVector getTermFreqVector(int docNumber, String field) throws IOException {
        ensureOpen();
        return in.getTermFreqVector(docNumber, field);
    }

    @Override
    public void getTermFreqVector(int docNumber, String field, TermVectorMapper mapper) throws IOException {
        ensureOpen();
        in.getTermFreqVector(docNumber, field, mapper);
    }

    @Override
    public void getTermFreqVector(int docNumber, TermVectorMapper mapper) throws IOException {
        ensureOpen();
        in.getTermFreqVector(docNumber, mapper);
    }

    @Override
    public int numDocs() {
        // Don't call ensureOpen() here (it could affect performance)
        return in.numDocs();
    }

    @Override
    public int maxDoc() {
        // Don't call ensureOpen() here (it could affect performance)
        return in.maxDoc();
    }

    @Override
    public Document document(int n, FieldSelector fieldSelector) throws CorruptIndexException, IOException {
        ensureOpen();
        return in.document(n, fieldSelector);
    }

    @Override
    public boolean isDeleted(int n) {
        // Don't call ensureOpen() here (it could affect performance)
        return in.isDeleted(n);
    }

    @Override
    public boolean hasDeletions() {
        ensureOpen();
        return in.hasDeletions();
    }

    @Override
    protected void doUndeleteAll() throws CorruptIndexException, IOException {
        in.undeleteAll();
    }

    @Override
    public boolean hasNorms(String field) throws IOException {
        ensureOpen();
        return in.hasNorms(field);
    }

    @Override
    public byte[] norms(String f) throws IOException {
        ensureOpen();
        return in.norms(f);
    }

    @Override
    public void norms(String f, byte[] bytes, int offset) throws IOException {
        ensureOpen();
        in.norms(f, bytes, offset);
    }

    @Override
    protected void doSetNorm(int d, String f, byte b) throws CorruptIndexException, IOException {
        in.setNorm(d, f, b);
    }

    @Override
    public TermEnum terms() throws IOException {
        ensureOpen();
        return in.terms();
    }

    @Override
    public TermEnum terms(Term t) throws IOException {
        ensureOpen();
        return in.terms(t);
    }

    @Override
    public int docFreq(Term t) throws IOException {
        ensureOpen();
        return in.docFreq(t);
    }

    @Override
    public TermDocs termDocs() throws IOException {
        ensureOpen();
        return in.termDocs();
    }

    @Override
    public TermDocs termDocs(Term term) throws IOException {
        ensureOpen();
        return in.termDocs(term);
    }

    @Override
    public TermPositions termPositions() throws IOException {
        ensureOpen();
        return in.termPositions();
    }

    @Override
    protected void doDelete(int n) throws CorruptIndexException, IOException {
        in.deleteDocument(n);
    }

    @Override
    protected void doCommit(Map<String, String> commitUserData) throws IOException {
        in.commit(commitUserData);
    }

    @Override
    protected void doClose() throws IOException {
        in.close();
    }

    @Override
    public Collection<String> getFieldNames(IndexReader.FieldOption fieldNames) {
        ensureOpen();
        return in.getFieldNames(fieldNames);
    }

    @Override
    public long getVersion() {
        ensureOpen();
        return in.getVersion();
    }

    @Override
    public boolean isCurrent() throws CorruptIndexException, IOException {
        ensureOpen();
        return in.isCurrent();
    }

    @Deprecated
    @Override
    public boolean isOptimized() {
        ensureOpen();
        return in.isOptimized();
    }

    @Override
    public IndexReader[] getSequentialSubReaders() {
        return in.getSequentialSubReaders();
    }

    @Override
    public Map<String, String> getCommitUserData() {
        return in.getCommitUserData();
    }

    /** If the subclass of FilteredIndexReader modifies the
     *  contents of the FieldCache, you must override this
     *  method to provide a different key */
    @Override
    public Object getCoreCacheKey() {
        return in.getCoreCacheKey();
    }

    /** If the subclass of FilteredIndexReader modifies the
     *  deleted docs, you must override this method to provide
     *  a different key */
    @Override
    public Object getDeletesCacheKey() {
        return in.getDeletesCacheKey();
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        final StringBuilder buffer = new StringBuilder("FilterReader(");
        buffer.append(in);
        buffer.append(')');
        return buffer.toString();
    }

    @Override
    public void addReaderFinishedListener(ReaderFinishedListener listener) {
        super.addReaderFinishedListener(listener);
        in.addReaderFinishedListener(listener);
    }

    @Override
    public void removeReaderFinishedListener(ReaderFinishedListener listener) {
        super.removeReaderFinishedListener(listener);
        in.removeReaderFinishedListener(listener);
    }
}
